Mountjoy K, Cowden E A, Dobbie J W, Ratcliffe J G
J Endocrinol. 1980 Oct;87(1):47-54. doi: 10.1677/joe.0.0870047.
Specific binding of 125I-labelled ovine prolactin iodinated by a lactoperoxidase method was demonstrated in crude membrane preparations of kidneys and adrenals of male Sprague-Dawley rats and livers from female rats. Membrane preparations derived from the 100,000 g fractions of tissue homogenates contained most of the specific prolactin binding. Kinetic and affinity characteristics of prolactin binding to kidney membranes were examined in detail. Maximal specific binding occurred after incubation for 30 h at room temperature. Scatchard analysis indicated that prolactin binding to kidney membranes was of high affinity (dissociation constant = 1.4 x 10(-10) mol/l) and similar to that for liver membranes, although kidney membranes from male rats bound approximately sixfold less prolactin/mg membrane protein than did liver membranes from female rats. Specific prolactin binding was demonstrated in both renal medulla and cortex. Autoradiography showed maximal prolactin binding activity in the epithelial cells of the proximal tubule and faint activity in the tubular cells throughout the nephron. Specificity of uptake by proximal tubular cells was indicated by the gross reduction in prolactin activity when excess ovine prolactin was administered simultaneously. The demonstration of specific binding sites for prolactin localized primarily in the proximal tubules was consistent with renal action of prolactin, predominantly on sodium metabolism.
通过乳过氧化物酶法碘化的125I标记的绵羊催乳素在雄性斯普拉格-道利大鼠的肾脏和肾上腺以及雌性大鼠的肝脏的粗膜制剂中显示出特异性结合。来自组织匀浆100,000 g级分的膜制剂含有大部分特异性催乳素结合。详细研究了催乳素与肾膜结合的动力学和亲和力特性。在室温下孵育30小时后出现最大特异性结合。Scatchard分析表明，催乳素与肾膜的结合具有高亲和力（解离常数= 1.4×10(-10) mol/l），与肝膜相似，尽管雄性大鼠的肾膜每毫克膜蛋白结合的催乳素比雌性大鼠的肝膜少约六倍。在肾髓质和皮质中均显示出特异性催乳素结合。放射自显影显示近端小管上皮细胞中催乳素结合活性最高，整个肾单位的肾小管细胞中活性较弱。当同时给予过量的绵羊催乳素时，催乳素活性大幅降低，表明近端小管细胞摄取具有特异性。催乳素特异性结合位点主要定位于近端小管，这与催乳素对肾脏的作用一致，主要作用于钠代谢。
